Meeting Abstract
22.1 Saturday, Jan. 4 13:45 Corticosterone receptor concentrations are correlated across different tissues within individual house sparrows (Passer domesticus) LATTIN, CR*; KENISTON, DE; ROMERO, LM; Tufts University; Yale University; Tufts University christine.lattin@tufts.edu
Hormonal mediators often show enormous intraspecific variation. Although there have been increased calls to make this individual variation the focus of inquiry, relatively few investigators have done so, especially with endocrine mediators other than hormone titers. For example, does an animal with high receptor density in one tissue also tend to have high receptor density in other tissues? We used a dataset of 72 house sparrows to examine individual correlations in glucocorticoid receptor binding (GR) and mineralocorticoid receptor binding (MR) across 14 different tissues: bib, back and belly skin, pectoralis and gastrocnemius muscles, subcutaneous and omental fat, liver, kidney, spleen, whole brain, hippocampus, testes and ovary. We used restricted maximum likelihood to estimate mixed models of receptor concentration with fixed effects at the tissue level and random effects at the bird level. Significance tests of random effects strongly rejected the null hypothesis of no bird-level variation in GR and MR. We also examined which receptor concentrations in individual tissues could be explained by receptor concentrations in all other tissues. For MR, we found hippocampus, kidney and throat fat most correlated with other tissues. No specific tissues showed significant GR receptor correlations with others. Back and belly skin receptor concentrations were consistently uncorrelated with other tissues, as were omental fat and pectoralis GR. These results clearly demonstrate that individual house sparrows tend to exhibit higher or lower sensitivity to CORT across all tissues, perhaps due to regulation of receptor concentrations by the common signal of circulating CORT. Receptors in tissues showing the lowest correlation with other tissues may be co-regulated by tissue-specific factors, such as local CORT production and the presence of metabolizing enzymes.
